Motor testing instrument



Nov. 21, 1933. 1,936,128

P. N. ELDERKIN MOTOR TESTING INSTRUMENT Filed March 5, 1929 3 Sheets-'Sheet l NVENTOA/ Afrox/vzw Nov. 21,1933. p. N. ELDERKIN 1,936,128

MOTOR TESTING INSTRUMENT Filed March 5, 1929 3 Sheets-Sheet 2 A TroRNeY Nov. 2l, 1933.

Low PREal'No/cAroe PRES. IND/carole P. N. ELDERKIN MOTOR TESTING INSTRUMENT Filed March 5, 1929 3 Sheets-Sheet 3 C we REN-r INDICATO/e Patented Nov. 21,*l953 Y unirse STATES PATENT OFFICE Application March 5, ,1929. Serial No. 344,541 `i claims. (C1. rus-183)v l This Yinvention relates kto meansV including Fig. 7 is. a bottom plan, orrreverse side of grouped and `interrelated agencies kfor complete the spark-gap device.v testing-of electrically-med internal combustion Fig.v Sshows a diagrammaticgview in isometric engines.` While adapted for testing motors which perspective of the apparatus with' all conduits' employ any working fluid,.iir.ed in any manner, and connections attached to different points of 6g the apparatus `is adapted for the complete testthermotor and ignition system for testing'. ing of carburetters and electrical equipment for rCertain features disclosed herein are claimed ignitionso that it is applicable to any electriin application led herewith, Y Serial Number cally-fired, internal vcombustion motor. 344541. f'

" 1 0 The object of the invention is to produce a lowf' In the specific form illustrated in the drawing-s, 65v

cost, reliable aggroupment of testing agencies the apparatus includes meansAfor measurement which, by their cot-ordination and individual charof relatively high pressures; means B for indiacteristics, adapt them'to rapid and effective decating relatively 10W pressure, `01 VaCllIlm; termination of all of the probable and usual demeans C for indicating current lIOW; means D rects inthe motor; the source of e1ectrica1 supply; for indicaties electrcmctive forces, and means E 70, the Aconducting system; the sparking devices; for determining sparkfgap conditions which is the electrical yauxiliaries and other parts which later described herein. -In the arrangement Shown relate to the motor; its pistons, valves and conin the drawings, allVe. 0f the ltefelalled'gennections, and to so group and arrange these agencies are located in a circular relationship being v2O cies'as tomake them compact, of small Weight, angularly disposed around auxiliary valve-regu- 75 5 5 indicator.

and if desired, easily portable, and, bythe employlatine means, e. The several agencies may be ment of a unitary combination or group,enables oi such a size and so related in the assembly that the operatorito discover the-exact conditions of While 6215113 readable,` and accurate in their in# the several'parts whichare'subject to wear and diCatOnS, they may 00.01195 Only 2' Small Space, derangeinent and to diagnose the condition of the and may be 0f COmpfIatVely Smalltoal Weight 80 motor, completely and definitely. and therefore'conveniently and easily hand-port- Ad-ditional objectswili be disclosed as this deable. i scription proceeds.v With the foregoing and other AS indicated in Fg- 3, the flat plate 0I dSC, H, objects in View the invention consists in the novel 011 Which the ageles are mounted, S -DIOVded and useiul formation, construction, interrelation l With Sides at right angles theretorlhreby OIIII- 85 and combination or parts, members and features, ins aholderfcr container. The connecting tubes au as hereinafter described, shown in the drawand Wires pass from their respective agencies t0 ings and nnally-pointed out in claims. 1 v appropriate locations on the motor or to the sev- In the drawings: i `eralelectrical parts and there are connected to 3.5 Fig. 1 is a plan view of the face of one or the theaeiernts cndwhich cgservatiins aretoe 90 preferrediorms of the apparatus, showingthe ma e; es? S31 00 111'160 mg Pa'f S, 0 1 .9X1 Si endsy of the respective conduits and connectors tubfs andiWlTeS/i passmg through the 51de ofthe for suitably connecting the different agencies to Vertlca'l members of the contamer 0T holder as appropriate parts oi the motor and the electrical mdlca'ted 'm the figures' equipment f Some of the separate cooperating agencies, A95 Y ,Y Fig. 2 is a side elevation of the apparatus mountgllhsncdh,agegrg tlslch shows a part of the Condults and'vcon' electricalV instruments, and the like, have some wip. Ottm'n 12m or upders'd .e f special arrangementv or construction .which y b lg' 910, p t, I elw W o adapts them for `the especial and cooperative 100 t -e appaiagtus snowing cer ain con ro va ves, the uses for which they are e p10yed Theymeans mmmtmg for the dlfferet agencles the. ends of A isI connected with any cylinder of the motor ghe conduits and connections and a testing conto be tested, by screwing the brass fixtures m elSef i at Ythe outer end'of the tube a over the outer Fig. t4 iS 2 SeCEl-lll eleVa'fOIl 0f the apparatus threaded nipple 11. of an adapter, such as is shown r105 0n S60 Ol #me i Y in Fig.k 5. Several adapters are suppliedrwith Fig. 5 is an elevation of an adapter, partlysecthe apparatus. The outer nipple end, n, of the tional. j adapter which screws into the brass fitting, m, Fig. 6 iS a pian 0fthe adjustable spark-gap on the end ofthe exible pipe, a, is V-the Asame sizeioreyery adapter, but the innerl threaded nipple, p, of each adapter differs in size and! threading from any of the others, there being an adapter having an inner nipple, p, to suit each kind or make of spark-plug hole. In making pressure tests on any motor, the means A may be quickly connected to any cylinder thereof, by simply screwing out the spark plug and screwing in its place the nipple end, p, 0f an adapter which fits in the spark plug hole. A check-valve in the adapter permits flow in one direction only, viz: outwardly, or away from the motor so that when the highest pressure is indicated in the cylinder to which the tube and its agency are connected, and the further movement of the motor piston diminishes the pressure, the reading of pressure on the suitably actuated indicating needle does not fall, but the maximum pressure, only, is registered. A needle valve, o, or equivalent constriction, is placed in the pipe line near the apparatus in order to prevent oscillation of the needle under quickly changing pressures; in other words, to make the indicating pointer dead-beat. Low pressure, or vacuum indicating means B is arranged to have the iiexible pipe, b, thereto attached, connected to the intake manifold, through an opening either previously made for the purpose, or that whereto the vacuum feed device is connected, may be used. There is a constricting valve, d, in the tubular conducting line from the manifold, immediately near the apparatus, which valve is controlled by a large button, or twisting member, e, as shown. Attached to this member, c, is a pointer, or needle, f, which revolves around a circle, g, engraved on the supporting plate and on which are graduations, usually from 0 to 100. The graduations have no speciic meaning, but serve to indicate, for any particular constricting valve, the approximate point where the related indicating needle becomes quiet and stops quivering under variable pressures.

The electrical indicating means C and D are constructed in accordance with the dArsonval galvanometer principle. Connected in parallel with the electromotive force indicator Dis condenser G, as shown. The spark gap device E is especially arranged, designed, calibrated and connected for the apparatus.

The adjustable gap has an indicator, t, which shows, not the actual distance apart of the electrodes, but the equivalent of the distance between them related to the compression pressure of the cylinder in which the spark plug is to operate. It is a well-known fact that the greater the ambient pressure in which a sparkgap works, the greater must be the voltage to send an electric current from terminal to terminal across a xed gap. Hence, a spark plug, tested at atmospheric pressure, may sparkunder the available voltage while, under the compression at which ringv occurs, the same voltage may not be able to force the current to jump the gap. It is by this method, of iirst finding the maximum compression pressure by use of agencyV A, and then fixing an equivalent gap, at atmospheric pressure, to determine whether the available electro-motive force is sufcient to produce sparking under actual operating pressure that the testing apparatus is made-'completely useful and suitable for diagnosing these parts of a motor ignition system.

Cooperating with this specially calibrated spark-gap and connected permanently in parallel therewith, is another specially designed device or agency, F, which comprises a small glass tube lled with a gas at an attenuated pressure, in fact only a fraction of the normal atmospheric pressure, and in which an electrode has been sealed at one end. A conductor passing out through the end of the tube provides a terminal to which connection can be made from a source of external electrical pressure to the electrode inside of the tube, so that this electrode with its attached conductor, forms one electrode. Near the end opposite from the electrode end, the tube has a band, or strap, of metal, par tially surrounding it which forms a support for the tube and acts as an electrode for the device, the passage of current being, of course, from inner electrode toattenuated gas, thence, by induction through the dielectric (glass) of the tube, to the outer strap or terminal.

Obviously, a considerable ow of current across the spark-gap of agency F will indicate a considerable electro-motive force across the terminals thereof, and, since this same electro-motive force is coincidently applied to the terminals of the tube, F, a iow of current will take place through the gas-illed, transparent device, so that the attenuated gas contained therein, will glow, the degree of its luminosity being proportional to the quantity of current and, therefore, to the impressed electro-motive force. Hence, by observation of the glass tube, when a voltage is applied to its terminals, some general idea of the said voltage may be obtained.

From this it follows that when the spark-gap elements are separated a distance equal to the normal separation of spark plug elements, plus such additional distance as is equal to the increased resistance proceeding from the compression of the ambient gases, the voltage necessary to cause sparking across the gap, will be great enough to produce a considerable flow through the gas-nlled tube and make it glow. Hence, the indications of this agency are additional to the separations of thevspark-gap elements, and observation of the degree of brilliancy, coincident- 1y with the observations of the sparking across 'the gap*its uniformity, and failure to cease or diminish-assists in determining the strength of the electro-motive force which is provided by the igniting system of the motor plant.

This sparking incicator is more clearly shown in Figs. 6 and 7. A case, l, having a bottom, 2, surrounds and supports the membersvand parts. The case is preferably cylindrical with a cover, 3, in which latter is fixed a transparent disc 4 so that the interior of the instrument may be observed therethrough. The spark-gap is made upef the two members w and whereof the former is adapted to be moved by the turning of a twisting member, 5, while w is fixed in position. w is the end of a movable arm pivoted at 6, which arm is. arranged to rotate about 6 by turning of the member 5. While any suitable form of mechanical connection may be used for causing the arm w to rotate about pivot 6, and, by its rotation, to change the spark-gap, the present preferred arrangement is that of a cam '7, mounted on the vertical shaft 8, as indicated by the dotted lines. As before explained, the graduated arc, t', on sector 9, attached to shaft 8, and, therefore, which revolves with 8, is graduated to show, by its relation to the fixed pointer, lc, a distance apart of the electrodes having a resistance to passage or" current equivalent to that of a non .al spark plug gap surrounded by a considerable pressure. Hence, by turning twisting member 5 and with secarse "it, the shaft 8, until the reading on the sector, t,

corresponds with the previously l`.found-pressure Atance loi the two spark-plug electrodes hy an amount which isedual to the diiierence between the resistance of the-spark plug `electrodes under the pressure found, and that which vwould exist under atmospheric pressure. This means, of course, that the separation ofthe gap parts and w is greaterv than the actual separation ci the spark plug parts, in order to make the two different gaps of equivalent resistance to passage 'of current.

The adjustable sp-arkegap and'hlow-tube `are so Vlocated that 'they areV visible simultaneously, they ybeing arranged for vision at the same instant and by the vsame observation. This device operates in conjunction with the compression agency A oy first testing Y,the compression of the cylinder, with its Valves and connections. Then the spark-gap is set so that the number onv th sector, 9, opposite the pointer, lc, indicating pressure, is identical with the pressure as found by the compression testragency. Then, if the elec- `trical equipment will pass sparks through the gap and, simultaneously, illumine the glow-tube, this proves that the electro-motive force is sufficient to produce agood spark under actual operm ating conditions and cylinder pressures.V

As an indication ofthe use of this no-vel combination oi agencies, a few ofthe tests'for which it j may be employed 'are set forth. l

To determine the condition of the piston and Vvalves of any ne cylinder unit, the compression agency'is iirst connected withthe spark plug opening'of the particular cylinder yunder observation, as shown in dotted lines in 8. The motor is then rotated at a slow speed hy an external agency, usually the electrical starter. On the compression stroke the degree.. of compression vwill be indicated on the instrument .and if piston rings and valves are all tight and in goodcondition, the maximum pressure indication will equal that whichV was originally produced `in the cylinder when the car was new and which is, usually, a known quantity.- Generally, however, the maxi- -mum pressure attained will 'be considerably less than that when the car wasnew. This proves only that leakage occurs but does not indicate the locality oi such leakage. By removing vthe tube connector, o, and the adapter, from :the spari: plug hole a' specially heavy oil is' ejected into the cylinder with an oil can, iavinga long curved spout, so that any leakagepast the piston rings is practically sealed, the instrument is re- -connectedto the same cylinder and, by external means,Y the vmotor is again rotated. if thev pres.

sure `observed on this-second test is higher than that observed on the iirst tes the difference, or

. increase, is obviously that which proceeded from loss around the piston rings, now eliminated. Therefore, the amount of this loss is now deri-1 nitely known. By subtracting this known loss from the previously iound total loss, the remainder is clearly that due to valve leakage. li the admission valve be ground so that it is den- Vnitely tight and without leak, and a'third test is made, it is obvious that, Vfrom the last set oitest iigures obtained, any Aleakage past the exhaust valves will hel definitely shown.

AA certain degree ci familiarity with the apparatus must be attained before rapid and accurate diagnosis oi al1 the parts of the motor can are far greater.

springs.

adjustment.

bemande. For instance, if the low pressure, ior

Vacuum, indicating means is connected with the 'engine intake manifold, the needle or pointer will move withv changeslin pressure in the manifold. AIfthe' motor beslowly turned over by some external means and it be found that at a certain point in the rotation the needle reaches some Vvalue and then slowly sinks h ck to some lower value, this is an indication of a leaky Valve. If al mere leaky valve, the rate of pressure drop and its degree, will be comparatively small, 'say` 4 or 5 Vdivisions in 5' to 10 seconds. If, however, the

valve is'hadly distorted, usually called a burnt valve, the rate of pressure change and its degree Ii lthe needle oscillates on both sides of 'some value which it reaches and the rate or" oscillation rincreases with the speed of the engine, this is a definite indicationv of one or more weak valve` i the same oscillation is observed Abut the movement is slow, and independent of the engine Vspeedthis shows aneed for carburetor adjustment and as the adjustment is made the needle will fluctuate more or less depending upon whether the direction of the adjustment is :towards or away from the corrective direction of From this can he determined the direction 'of change inthe adjustment, and if the adjustment be continued until the needle becomes steady, then the carburetor has been perfectly adjusted.

rEhese are simply examples of tests which may .be made'with this single agency of the apparatus,

there being actually eight separate and definite indications obtainable from it, and when the deyEects it shows are corrected, the needle will reach some point, near the middle of. the arbitrary scale, and there remain without movement vin either direction.

There are also tests for the combined low pressure agencyand the other agencies as mentioned later herein. p v

The'electrical agencies, including standardized condenser G, connected in parallel Vwith electro motive force indicator, D, and the adjustable spark-gap, E, with its special calibration and the luminous tube, F, connected in parallel with it, are used to. test the condition of the various electrical of the engine ignition devices. By

these coordinated agencies, practicallyany derect in the motor o-r the electrical equipment provided for the ignition of the gases, can he,Y quietly, surely and deilnitely determined.

In Figure 8 is shown one oi 'the methods of connecting the apparatus with the diierefnt parts ci the moto-r and its electrical ring equipment for making ceJtain of the tests, of which this-ap paratus is capable. The conducting tubesc and b which lead from their respective pressure indicators A and B are shown in dotted lines Vin order to indicate Ythe method of using these particular devices. These tubular conduits are seldom connected with the motor at the same time that the other devices are, and for this reason,

and in order to show the several points and meth ods of connection, tu'oesu ande are dotted in to indicate that they are not in use, orconnected with the motor, when the other portions of the apparatus are applied to the vaiiety of tests ior which they are adapted. f

The pressure-indicating agency, A, is connected withany cylinder of the motor, as `previously explained, by removing a spark plug, substituting an adapter (see Fig. 5), and connecting the con,- duit, a, with the adapter yas shown in the dotted lines. Likewise, the low-pressure indicating agency, B, is connected to the motor manifold, M, through tubular conduit, b, which usually is fastened to the opening made for the reception of the Vacuum feed. This connection is likewise indicated in the dotted lines.

For the electrical determinations covering investigation of the condition of the spark plugs; the condition of the condenser connected with the motor breaker; the current output passing through the primary coil and the breaker; the condition of the spark coils, both primary and secondary; the condition of the breakery points and such similar tests, the connections are shown in Figure 8. IThe di'erent operating parts of the electrical firing system are diagrammatically indicated and are disposed in position arbitrarily and in such manner as to make the conduits more easily traceable, the locations of these said parts not conforming in any manner to the actual positons of such parts either in a stationary motor equipment or that of a gasolinedriven motor car. 20 is the battery, 2l the positive terminal, 23 the primary of the spark coil connected to the tern minal 21 of the battery by wire 22. The other end of the spark coil 23 is connected by wire 24 to the current indicating agency C and the re-` turn circuit from this agency begins at terminal 26 thereof and is carried by wire 27 to the breaker member 28 having the contact point 29 which cooperates with the other contact member 3G. The latter is connected to a common conductor, such vas a motor-car frame, or the ground, by wire 3l. The other terminal of the battery 33 is connected by wire 32 to the saine common conductor, or ground, as indicated. Obviously, potential of breaker contact element 30 is identical with that of battery terminal 33. The wire 27 also connects with condenser 35, it branching at point 3e to this latter device so that one terminal of the condenser is at the same potential as breaker point 29. The opposite terminal is connected by wire 36 to ground so that the condenser is connected across the two breaker points. By tracing these circuits it will be found that there is a complete circuit from the battery through the primary coil through the current flow indicator, thence through the breaker and back to the op1 posite pole of the battery. rThis part o-f the system is customarily of low voltage, the standard being six volts, and all of the parts and wiring are constructed, designed and insulated for this low potential.

The high potential side oi the system begins with secondary coil 38 connected at one end by wire 37 to ground, and at the other end by wire 39 to the combined spark-gap and glow-tube apparatus, E. The circuit passing through this combined agency returns through wire 49 to the distributor 5S, the connections being arranged so that this distributor is in series with the high tension line passing through both the spark plug and the spark gap agency E, as will be seen by following the circuit from wire e9 where it enters distributor 5G, passes out of one of the distributor openings 51 and by wire 52 goes to spark plug 53, which latter has one side grounded by the mere fact that it is screwed into the metal of the motor, but it is here indicated as connected with ground by wire 54. Obviously, the upper end of the high tension secondary coil is at the same potential as one spark plug electrode and the high tension induced in this secondary coil by the action of the breaker is absorbed by driving the current through the circuit which includes the spark plug gap plus the spark-gap testing device, E, and the glow-tube; the two latter being `in parallel and this parallel pair being in series with the spark plug.

An additional connection is that of the electrical pressure-indicating agency, D,. having connected in parallel therewith the standardized test condenser G. The circuit across which these two agencies are connected begins on one side at ground, wire 58 connecting these two instruments to ground on one side, while wire 56 connects the other side of this pair of agencies to breaker element 28 and breaker contact point 29, wire 56 joining with wire 27 at junction point 55. Obviously, the side of the pressure-indicating agency, D, connected with ground is at the saine potential as that or" breaker contact point 30 and also of one side of the condenser 35. Hence the two condensers 35 and G, the former of which is a part of the motor apparatus, the latter a portion of the test apparatus, are connected in parallel.

While it is not the intention to extend this specification and make it unnecessarily long'by describing all of the possible tests, it is suitable to indicate a few which will indicate the utility of the apparatus. One of the tests is to determine the condition of the condenser 35 used in the motor ignition system. These condensers are subject to deterioration and may be defective even when new. To bein good operating condition they must have a reasonable capacity for the functionthey are to perform, namely, to permit substantially instantaneous breaking of the arc between the breaker points.; must be free from leakage, grounds or other defects. Without the condenser, the voltage induced in the secondary coil by the opening of the breaker points 'would be comparatively small. The voltage is induced by reason of the change in the current iiow through the primary coil, and the more rapid this current change the greater will berthe voltage induced in the secondary, higl1-tension coil. If no condenser were connected across the breaker points the interruption of current iiow would be comparatively slow, in fact might not take place at all, because as the breaker points begin to separate the tendency is for the current to now across the gap and form an arc, just as in the case of an ordinary arc lamp. This might be suicient to permit current iiow to continue throughout the period of separation of the two breaker elements. At any rate this tendency to form the arc would persist over a portion of the path of separation of the two breaker elements, which means that the time period of current interruption would be comparatively low. As is well known inthe art, a condenser connected across a'break of this character tends to extinguish the arc or prevent its formation and cause an almost immediate cessation of current flow when the breaker points begin to open. Therefore, a aulty condenser or one of insuflicient capacity will tend to prolong the time of current ilow and thereby diminish the l voltage in the secondary coil.

With the connections made as indicated in Fig. 8, the variable spark-gap-device, E, is set with the contact closed, so that it interposes no resistance, or spark-gap, in the circuit, and the ignition system is in its normal condition for operation. rEhe act ci testing comprises starting the motor and running it idle at about 250 R. P. M. While running, temporarily disconnect one of the wires tothe agency, D, either tinue toy open this spark-gap until there appears l to be a skip orfailure in engine firing on one or more cylinders Obviously, when this condition occurs the resistance to current flow throughthe path which includes the spark-gap of agency, E, and that of thesparkplug, has .become so great that the voltage of the system*Y is just able to pass necessary iiring current. through some of the .spark-plugs., When this condition isl obtained the temporarily removed connection from the agency lli, say wire- 58, is restored. When this is done it means that the condenser G connected with agency D, is connected in parallel with the condenser 35, so that, regardless of the characteristics of condenser 35, a standard condenser is now connected across the breaker points. lf', under this condition, the previous skip, or failure of some of the spark-plugs to fire, ceases, and the firing again becomes smooth, normal and regular, this change will be obviously due to the fact that the standardized external condenser G has replaced, in function, the condenser 35 bclonging to the engine equipment, and this, of course, is proof of the insufficiency of condenser 35.

While a description of the connections and this one test have occupiedy considerable space, in the hands of an expert this apparatus is connected, the tests made and the determinations therefrom reached, within a very short period of time and which is in no Wise related to the length of this explanation.

With this same series of connections, testsA of the ignition coils may be made. These coils, `iust as are Vcondensersare subject to deterioration, and may be defective when new, and many `failures of internal combustion engines to give sufcient power are due to defects in the spark coils. En order to test these coils it is iirst necessary to connect agency A' through tubular conduit, a, and adapter to the different cylinders of the engine successively as before explained and in the manner before described to determine the maximum compression pressure obtainable from each cylinder. When this is done the tubular connector, a, and adapter are removed, the spark plugs are replaced and the motor is started and run at the usual idling speed, about 250 R. P. M. At the time of starting the motor, the spark-meter agency E is set with the two elements thereof inv contact so that it interposes no gap or resistance in the circuit and the electric ignition system operates as usual. After the motor has been brought up to idling speed and has run a few seconds, the spark-meter dial is turned until the pointer indicates on the grad- `uated segment the iigure representing the corcpression as obtained from the previous test. The spark-meter gap, and the luminous glass tube are both observed. If the spark across the gap is continuous and free from skips, and the flash in the gas tube is continuous and bright, then this test shows that the coils are in good condition. But if the sparks across the gap skip or falter, and the glovv inthe tube becomesv darkened, particularly near one end, the coils are defective. If the engine stops, of course, this is an Yindication that thercoils are wholly unusable in any manner. Y

The more important tests which can be made rapidly and quickly with this novel apparatusl are (l) ignition coil tests; A(2) calibration of electrical instruments forming Ypart .of thel engin( firing system; (3) location of short circuits, open circuits and grounds;l (-4) determination'of condition ofbreaker pointsy'iv.) a testof the storagebattery,gitscondition.andY output; (A6) condition of condensers; (7) condition of `each spark plug; (8)y determination of condition of wiring particularly with relation to leaking, high tension conductors. frequent cause of unsatisfactory operation, and, usually difficult to locate, but is indicated almost immediately y the use of this apparatus); l(9) condition of 'valvesshovving whether. they. are. burnt,distcrtedrleaky, sticky, whether they have loose valve guides, weak valve springs or late timing; (lo) adjustmentof carburetonand (11) test of condition of pistons. Of course, other forms of tests will suggest themselves to those skilled in the internal combustion engine and affiliated arts.

vBut certain of the tests require the use of more than one agency. For instance, as before mentioned, in determination of the ignition voltage of the electrical system and its sufficiency or inadequateness, it is lrst' necessary to find the maximum compression by use of the compression indicating means, then set the sparks-gap adjustment to correspond with this determined pressure and from the behavior of this. sparkgap and electrically attached luminous tube, to determine the sufficiency or inadequacy of the oscillatory or pulsating voltage impressed on the spark plugs. Y

It is obvious, therefore, that this nal result is obtainable only by two successive tests made through agencies arranged in juxtaposition for such trials.

Having described my invention in connection with illustrative embodiments, forms, proportions, arrangement of parts and orders of steps, it will be understood that many variants thereof are possible to those skilled in the art, and my invention, in its broader aspects, is not limited to the specific construction herein described and shown, as changes in the sizes, proportions, congurations, arrangements, assemblage, interaction, juxtaposition and mechanical relations, as well as additions, omissions, substitutions, combinations and alterations of forms, parts, members and features, and in the kind and order of operations and successive steps, may be made Without departing from the broad spirit of this invention.

Having thus disclosed my invention, I claim and desire to secure by Letters Patent:

1. A testing device for internal combustion engines comprising, in combination, a unitary assembly of simultaneously visible means for indicating the cylinder pressure of the engine, means for indicating the correct spacing of the points of the spark plugs of the engine for a given cylinder pressure, and means to indicate whether the points of the spark plugs are so spaced that a spark will be produced thereacross under the cylinder pressure indicated. s

2. A testing device for internal combustion engines comprising, in combination, a unitary assembly of simultaneously visible means for indicating the cylinder pressure of the engine, and means for indicating whethery the points of the spark plugs of the engine are so spaced that the available current of the ignition system of the engine is effective under the cylinder pressure indicated to produce a spark across the gap between (This is a common fault, is a.

the spark plug points in the normal operation of the engine.

3. A testing device for internal combustion engines comprising, in combination, a unitary Vassembly of simultaneously visible means for indicating the cylinder pressure of the engine, and means for indicating the correct spacing of the points of the spark plugs of the engine to assure that a spark will be produced across said points under the cylinder pressure indicated and under normal operating conditions of the engine.

4. A testing device for internal combustion engines comprising in combination, a casing, means Within said casing for indicating the cylinder pressure of the engine, and means Within said casing for indicating whether the points 'of the spark plugs of the engine are so spaced that the available current of the ignition system of the engine is eiective under the cylinder pressure indicated oy said :first mentioned means to produce a spark across the gap between the spark plug points during normal operation of the engine, said cylinder pressure and said spark gap indicating means being located relatively close together to be viewed simultaneously throughone face of the casing to facilitate use of the second mentioned means in View of the indications of the rst mentioned means.

PAUL N. ELDERKIN. 

